-fms-extensions: Implement half of #pragma init_seg

Summary:
This pragma is very rare.  We could *hypothetically* lower some uses of
it down to @llvm.global_ctors, but given that GlobalOpt isn't able to
optimize prioritized global ctors today, there's really no point.

If we wanted to do this in the future, I would check if the section used
in the pragma started with ".CRT$XC" and had up to two characters after
it.  Those two characters could form the 16-bit initialization priority
that we support in @llvm.global_ctors.  We would have to teach LLVM to
lower prioritized global ctors on COFF as well.

This should let us compile some silly uses of this pragma in WebKit /
Blink.

Reviewers: rsmith, majnemer

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4549

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@213593 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 72 insertions, 16 deletions

diff --git a/test/CodeGenCXX/pragma-init_seg.cpp b/test/CodeGenCXX/pragma-init_seg.cpp
index 7356c52aa3..3f9ff217e6 100644
--- a/test/CodeGenCXX/pragma-init_seg.cpp
+++ b/test/CodeGenCXX/pragma-init_seg.cpp
@@ -1,16 +1,72 @@
-// RUN: not %clang_cc1 %s -triple=i686-pc-win32 -fms-extensions -emit-llvm-only 2>&1 | FileCheck %s
-
-// Reduced from WebKit.
-
-// FIXME: Implement this pragma and test the codegen.  We probably want to
-// completely skip @llvm.global_ctors and just create global function pointers
-// to the initializer with the right section.
-
-// CHECK: '#pragma init_seg' not implemented
-#pragma init_seg(".unwantedstaticinits")
-struct A {
-  A();
-  ~A();
-  int a;
-};
-A a;
+// RUN: %clang_cc1 %s -triple=i686-pc-win32 -fms-extensions -emit-llvm -o - | FileCheck %s
+
+int f();
+
+// CHECK: $"\01?x@selectany_init@@3HA" = comdat any
+// CHECK: $"\01?x@?$A@H@explicit_template_instantiation@@2HB" = comdat any
+// CHECK: $"\01?x@?$A@H@implicit_template_instantiation@@2HB" = comdat any
+
+namespace simple_init {
+#pragma init_seg(compiler)
+int x = f();
+// CHECK: @"\01?x@simple_init@@3HA" = global i32 0, align 4
+// CHECK: @__cxx_init_fn_ptr = private constant void ()* @"\01??__Ex@simple_init@@YAXXZ", section ".CRT$XCC"
+
+#pragma init_seg(lib)
+int y = f();
+// CHECK: @"\01?y@simple_init@@3HA" = global i32 0, align 4
+// CHECK: @__cxx_init_fn_ptr1 = private constant void ()* @"\01??__Ey@simple_init@@YAXXZ", section ".CRT$XCL"
+
+#pragma init_seg(user)
+int z = f();
+// CHECK: @"\01?z@simple_init@@3HA" = global i32 0, align 4
+// No function pointer!  This one goes on @llvm.global_ctors.
+}
+
+#pragma init_seg(".asdf")
+
+namespace internal_init {
+namespace {
+int x = f();
+// CHECK: @"\01?x@?A@internal_init@@3HA" = internal global i32 0, align 4
+// CHECK: @__cxx_init_fn_ptr2 = private constant void ()* @"\01??__Ex@?A@internal_init@@YAXXZ", section ".asdf"
+}
+}
+
+namespace selectany_init {
+int __declspec(selectany) x = f();
+// CHECK: @"\01?x@selectany_init@@3HA" = weak_odr global i32 0, comdat $"\01?x@selectany_init@@3HA", align 4
+// CHECK: @__cxx_init_fn_ptr3 = private constant void ()* @"\01??__Ex@selectany_init@@YAXXZ", section ".asdf", comdat $"\01?x@selectany_init@@3HA"
+}
+
+namespace explicit_template_instantiation {
+template <typename T> struct A { static const int x; };
+template <typename T> const int A<T>::x = f();
+template struct A<int>;
+// CHECK: @"\01?x@?$A@H@explicit_template_instantiation@@2HB" = weak_odr global i32 0, comdat $"\01?x@?$A@H@explicit_template_instantiation@@2HB", align 4
+// CHECK: @__cxx_init_fn_ptr4 = private constant void ()* @"\01??__Ex@?$A@H@explicit_template_instantiation@@2HB@YAXXZ", section ".asdf", comdat $"\01?x@?$A@H@explicit_template_instantiation@@2HB"
+}
+
+namespace implicit_template_instantiation {
+template <typename T> struct A { static const int x; };
+template <typename T> const int A<T>::x = f();
+int g() { return A<int>::x; }
+// CHECK: @"\01?x@?$A@H@implicit_template_instantiation@@2HB" = linkonce_odr global i32 0, comdat $"\01?x@?$A@H@implicit_template_instantiation@@2HB", align 4
+// CHECK: @__cxx_init_fn_ptr5 = private constant void ()* @"\01??__Ex@?$A@H@implicit_template_instantiation@@2HB@YAXXZ", section ".asdf", comdat $"\01?x@?$A@H@implicit_template_instantiation@@2HB"
+}
+
+// ... and here's where we emitted user level ctors.
+// CHECK: @llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }]
+// CHECK: [{ i32, void ()*, i8* } { i32 65535, void ()* @_GLOBAL__sub_I_pragma_init_seg.cpp, i8* null }]
+
+// We have to mark everything used so we can survive globalopt, even through
+// LTO.  There's no way LLVM could really understand if data in the .asdf
+// section is really used or dead.
+//
+// CHECK: @llvm.used = appending global [6 x i8*]
+// CHECK: [i8* bitcast (void ()** @__cxx_init_fn_ptr to i8*),
+// CHECK: i8* bitcast (void ()** @__cxx_init_fn_ptr1 to i8*),
+// CHECK: i8* bitcast (void ()** @__cxx_init_fn_ptr2 to i8*),
+// CHECK: i8* bitcast (void ()** @__cxx_init_fn_ptr3 to i8*),
+// CHECK: i8* bitcast (void ()** @__cxx_init_fn_ptr4 to i8*),
+// CHECK: i8* bitcast (void ()** @__cxx_init_fn_ptr5 to i8*)], section "llvm.metadata"